Sustainable Stabilization of Landfill Mined Soil-like Fraction with Alkali Activated Slag for Pavement Infrastructure Applications

Abstract

Landfill mined soil-like fraction (LMSF) constitutes a significant portion of waste mined from old un-engineered landfills. With the possible presence of organic matter, heavy metals and other hazardous components, the reutilization of LMSF is very limited. However, by adopting suitable treatment technologies, LMSF has great potential for reutilization as a material resource in infrastructure applications. The present study evaluates the performance of LMSF stabilized with alkali activated slag (AAS) with emphasis on its potential utilization as pavement subbase and base course material. The mechanical, durability and microstructural characteristics of the AAS-stabilized LMSF were evaluated and the results suggest that the AAS-stabilized LMSF combination with 40% binder replacement (34% ground granulated blast furnace slag (GGBS) and 6% activator with sodium hydroxide to sodium silicate ratio of 1:1.5) yields the best performance (unconfined compressive strength (UCS) value of 7.2 MPa at 28-days curing, with 3.2% cumulative mass loss after exposure to 12 wetting-drying cycles). The prolonged inundation in acidic and alkaline conditions reduced the 28-day UCS values for stabilized LMSF by about 28–38% and 35–45%, respectively; however, the residual UCS satisfied the strength requirements of most regulatory standards. Microstructural assessment conducted through X-Ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Thermogravimetric analysis (TGA), optical imaging and scanning electron microscopy (SEM) techniques revealed the presence of stable cementitious bonds in the stabilized LMSF matrix. Moreover, sustainability assessment revealed that AAS binder used in this study is about 6.5 times more sustainable than conventional cement stabilization. Overall, the current research provides valuable insights into the potential of LMSF as an alternate material and provides a pathway towards achieving United Nations sustainable development goals.